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Slide 3 ILLINOIS - RAILROAD ENGINEERING Overview of railroad hazardous materials transportation There were 1.7 million rail carloads of hazardous materials (hazmat) in the U.S. in 2010 (AAR, 2011) Hazmat traffic account for a small proportion of total rail carloads, but its safety have been placed a high priority

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Slide 8 ILLINOIS - RAILROAD ENGINEERING Uncertainties in hazmat risk assessment The evaluation of hazmat release risk is dependent on a number of parameters, such as –train derailment rate –car derailment probability –conditional probability of release etc. The true value of each parameter is unknown and could be estimated based on sample data The difference between the estimated parameter and the true value of the parameter is measured by standard error

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Slide 19 ILLINOIS - RAILROAD ENGINEERING Risk comparison under uncertainty The uncertainty in the risk assessment should be taken into account to compare different risks For example, assuming a baseline route has estimated risk 0.3, an alternative route has estimated risk 0.5, is this difference large enough to conclude that the two routes have different safety performance? –It depends on the standard error of risk estimate on each route

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Slide 21 ILLINOIS - RAILROAD ENGINEERING Conclusions Risk analysis of railroad hazmat transportation is subject to uncertainty due to statistical inference based on sample data These uncertainties affect the reliability of risk estimate and corresponding decision making In addition to single-point risk estimate, its standard error and confidence interval should also be quantified and incorporated into the safety management